Equipment information:

The Model 415 Micro-microammeter incorporates advanced
high-speed circuitry developed by Keithley Instruments for rocket
and satellite experimentation -- where measurements of Lyman-
Alpha night slow, cosmic radiation, and upper air density require
fast response,
The 415 also provides zero suppression up to 100 full scales,
permitting full scale display of one per count variations of a
signal, or suppression of a steady background signal.